1. Field of the Invention
This invention pertains to a low ash mineral lubricating oil composition intended for use as a motor oil in an internal combusion engine. Internal combustion engines employed in short driving trips involving cold engine operation are subject to extensive rusting of the engine parts. This type of service does not permit adequate engine warm-up which is necessary to remove the moisture which has condensed in the engine. To overcome this serious rusting tendency, a lubricating oil composition has previously been developed containing a highly effective rust inhibitor when employed in a low ash mineral lubricating oil composition. The rust inhibitor, generically described as a hydrocarbyl-substituted trialkanolamine, permits the formulation of a motor oil composition which will pass the required MS IIC Rust Test.
Whle the foregoing lubricating oil composition substantially overcame the rust problem associated with cold engine operation, this lubricant was deficient with respect to weight losses of connecting rod bearings as determined by the CLR L-38 Test. The additive combination which exhibited the outstanding rust inhibiting properties was identified as the causative agent leading to the serious bearing weight losses.
It has now been discovered that the noted low ash, rust inhibited lubricating oil composition can be modified to substantially reduce the engine bearing weight losses while retaining the desirable low ash, rust inhibiting properties.
2. DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 1,888,023 discloses a color-stabilized lubricating oil composition containing a primary, secondary or tertiary aliphatic amine or hydroxyalkylamine.
U.S. Pat. No. 2,353,830 discloses a lubricant for an air pump containing triethanolamine stearate and comprising 80 percent of water.
U.S. Pat. No. 3,458,444 discloses a rust inhibited mineral lubricating oil composition containing the reaction product of an alkenylsuccinic acid or anhydride and an N-hydrocarbyl diethanolamine.
A copending application Ser. No. 424,978 filed on Dec. 14, 1973 now abandoned discloses a low ash lubricating oil composition containing a hydrocarbyl substituted trialkanolamine which qualifies the lubricant in the MS-IIC Engine Rust Test. This disclosure is being relied upon and incorporated in this invention.